1. Field of the Invention
This invention relates to video monitoring systems applied to systems such as security systems, industrial television (ITV) systems, etc., and more particularly to a video monitoring system applied to an environment where a communication path between a sending station which acquires the video signal and a receiving station which receives and monitors the video signal by means of a display or the like is established only when monitoring the video signal is required.
2. Description of the Related Art
A conventional video monitoring system has a dedicated transmission path fixedly provided between the sending station and the receiving station.
However, according to the conventional video monitoring system, the transmission path is always established even in an ordinary state where monitoring is not required.
At present, a video monitoring system has been considered in which there is provided a switching networks for selectively connecting the sending station and the receiving station only when monitoring the video is required.
However, in such system the establishment of a communication path (telephonic communication path) through the switching network takes considerably long time. Therefore, although the establishment of the communication path is started immediately after the occurrence of a particular event to be monitored such as an abnormality is detected, it is impossible to monitor the most important video images during the initial period of occurrence of the event. In other words, monitoring of the video images becomes possible after the communication path has been established, and therefore monitoring is not from the occurrence of the event, but from the establishment of the communication path.
In case that the video monitoring system is used in a security system, only video images generated some time after invasion of a robber can be monitored by the receiving station. In case that the video monitoring system is used in an ITV system, only video images generated some time after the occurrence of abnormality can be monitored. Accordingly, such monitoring systems cannot provide important video images to be monitored.